Add NullCheck for #657 fixes #663

common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11to1_10/ItemRewriter.java

@@ -97,7 +97,7 @@ public class ItemRewriter {
                 }
             }
         }
-        if (item.getAmount() <= 0) item.setAmount((byte) 1);
+        if (item != null && item.getAmount() <= 0) item.setAmount((byte) 1);
     }
 
     public static void toServer(Item item) {